Electrospray device

ABSTRACT

The invention related to a device ( 1 ) for spraying charged droplets of a liquid towards a target along a spraying direction, comprising: a reservoir ( 10 ) for storing the liquid (L), a first electrode ( 100 ) being arranged at an outlet ( 11 ) of said reservoir ( 10 ), a second electrode ( 200 ) forming a counter electrode to the first electrode ( 100 ) for accelerating said droplets (D) along the spraying direction (S), and a housing ( 30 ) holding the reservoir ( 10 ) as well as said electrodes ( 100, 200 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

This is the U.S. National Stage of International Application No.PCT/EP2013/067849, filed Aug. 28, 2013, which was published in Englishunder PCT Article 21(2), which in turn claims the benefit of EuropeanPatent Application No. 12181986.6, filed Aug. 28, 2012.

The invention relates to a device for spraying charged droplets of aliquid towards a target along a spraying direction, particularly so asto deliver said liquid or a substance contained therein into a cell or aplurality of cells forming said target. I.e. the respective cellmembrane is particularly overcome for delivering said liquid/substanceinto the respective cell (without destroying the cell).

Idiopathic pulmonary fibrosis (IPF) is a devastating disease affectingthe distal lung. It is suggested that the failure of the alveolarepithelium to heal after micro-injuries triggers complex biologicalprocesses, causing excess collagen deposition, leading to inefficientgas exchange leading to death. Current development looks at gene anddrug delivery to the distal lung, with a focus on gene therapy for thetreatment of IPF, using hepatocyte growth factor (HGF) for alveolar cellrepair and regeneration to reduce fibrosis [1].

A major challenge in gene therapy is the delivery of the substances intoliving cells avoiding side effects. The cell membrane offers a powerfulbarrier to protect the interior of the cells from any intruders. Forgene therapy this membrane has to be conquered effectively. There aredifferent procedures for gene transfer, based on viral vectors andnonviral methods. Transduction uses viruses, which host the gene andintroduce it as a part of their replication cycle. However, prominentlocal and systemic inflammatory and immunogenic response, leading toviral vector toxicity, restricts the clinical application of thissystem. In contrast non-viral methods such as the use of short andintense electrical pulses (ranging from microseconds to milliseconds;kilovolts per centimeter) applied to cells or tissues,‘electroporation’, offers a different mechanism for substances to enterthe interior of cells. As a response to an electrical field, the cellmembrane temporarily loses its semipermeable properties, leading to ionexchange, the escape of metabolites and an increased uptake of drugs,molecular probes, and genes. The feasibility of electroporation forsustained gene expression in vivo has been show previously in variousorgans including the lung.

Nevertheless the use of electroporation in therapeutic instruments seemsto be limited. To our knowledge, there is currently only one device indevelopment utilizing the electroporation effect to deliver anti-cancerdrugs to intraluminal tissue for electro-chemotherapy [2].

Further, nonviral gene transfer of substances into cells (transfection)may be performed by the use of an electrospray process [3, 4], in whichlikely charged droplets are accelerated towards an oppositely chargedelectrode by an electrical field. In addition, the likely chargeddroplets are affected by Coulomb repulsion. Further, a formation ofsmall droplets is caused by “Coulomb explosion” or “Coulomb fission”,wherein said Coulomb repulsion is (among others) responsible for thedistribution of the formed droplets.

The electrode nearby the targeted tissue guides a droplet bombardmenttowards the tissue, providing a high impact velocity for the collisionwith the cell membrane. The feasibility of this process for transfectionhas already been demonstrated by using water droplets [3], a plasmidsuspension incorporating gold nanoparticles [4], as well as a pureplasmid suspension[4]. However, these concepts rely on the requirementof a counter electrode at or below the target plate, thus yielding a setup that is less suitable for clinical practice.

For instance, US 2009/088700 A 1 teaches how to use an electrospraywithin the human body using a tubular device. However, the targetedtissue is grounded via an external electrode connected to the patientand therefore does not provide a single port access toward the region ofinterest. Furthermore, it does not offer a defined working distancebetween the human body and the device, and therefore it might bedifficult to control the spray process precisely, leading to anunspecified electrospray process and consequently a poorly controlledtransfection efficiency.

Therefore, the problem underlying the present invention is to providefor an improved electrospray device, particularly regarding clinicalpractice.

This problem is solved by a device having the features of claim 1.

According thereto, the claimed device is designed to spray chargeddroplets of a liquid towards a target along a spraying direction,particularly so as to deliver said liquid or a substance containedtherein into a cell or a plurality of cells forming said target, whereinparticularly the cell membrane of the respective cell is overcome due tothe impact energy of said droplets (which may optionally enhanced byusing electroporation), such that the liquid/substance can be deliveredinto the respective cell without destroying the latter. The deviceaccording to the invention further comprises a reservoir (e.g. somevolume) for receiving/delivering the liquid to be sprayed, a firstelectrode being arranged at an outlet of said reservoir for electrifyinga meniscus of said liquid at said outlet, at least one second electrodeforming a counter electrode to the first electrode for accelerating saiddroplets due to an electric field between said first and secondelectrode, and a housing holding the reservoir as well as saidelectrodes. When being in contact with the tissue, the tissue itselfforms part of the second electrode, i.e. a counter electrode.

According to a further embodiment of the invention, an end region of thesecond electrode, which may form a contact area (interface) for thetargeted tissue, is spaced apart from said outlet (or from said firstelectrode) along the spraying direction. Thus, a pre-definedacceleration stage can be provided for a controlled acceleration of thedroplet to be electrosprayed.

According to a further embodiment of the invention, said housingcomprises a spray chamber (cavity) extending along the sprayingdirection, wherein the reservoir is connected to the spray chamber viasaid outlet that opens into/towards the spray chamber, and wherein thespray chamber comprises an opening facing said outlet along the sprayingdirection for ejecting the droplets out of the spray chamber. Thus,arranging said opening at or close to the target (tissue) yields apre-defined working distance of the device allowing for a reproducibleelectrospray process.

According to a further embodiment of the invention, the first electrodecomprises a tubular shape and may be formed (at least in sections) as ahollow circular cylinder, wherein particularly the first electrode isdesigned to encompass the liquid in the reservoir or to delimit theoutlet of the reservoir. Particularly, the first electrode is made of aconducting material and forms said reservoir or at least a sectionthereof or may be formed as a conducting coating (or element) of thereservoir.

According to a further embodiment of the invention, the first electrodemay be coated or covered with an electrically isolating material.

Particularly, said outlet may form a nozzle for supporting spraying ofsaid droplets. Further, the reservoir may comprise a plurality ofoutlets, each being preferably delimited (surrounded) by a region of thefirst electrode.

According to yet another embodiment of the invention, the firstelectrode projects into the spray chamber. Particularly, the firstelectrode may comprise a region or section arranged on an inside of thespray chamber, which inside extends along the spraying direction,wherein particularly said region may circulate along said inside acrossthe spraying direction.

According to a further embodiment of the invention, the second electrodeis arranged at least in sections on a face side of the housingdelimiting said opening.

Particularly, in this regard, the second electrode forms a contact areabeing designed to contact said target onto which said liquid is to besprayed, so that the target (tissue) has the same potential as thesecond electrode, and thus actually forms (a part) of the secondelectrode.

Further, said contact area may have a microstructure allowing for animproved removal of liquid gathering between the contact area and thetarget. Herewith, an accumulation of liquid on the bottom (target) thatmay be caused by a continuous delivery of liquid to the target can bereduced. Such an unwanted accumulation of liquid is likely to result ina change of the electrical field, which increases the risk of anelectrical discharge. Furthermore droplets have to overcome this fluidicbarrier. This will lead to a reduced impact velocity and a lowertransfection rate. Further, to overcome this issue the amount of fluidto be delivered to the target can be reduced.

In order to prevent the afore-mentioned unwanted accumulation of liquid,the spray chamber may comprise a plurality of lateral through-holesaccording to a further embodiment of the invention. Liquid thataccumulates inside the spray chamber can then be discharged through saidlateral holes

In an alternative embodiment, the second electrode may comprise acircumferential free end region protruding from or out of the spraychamber towards the target (e.g. human tissue), wherein preferably saidfree end region comprises or consists of an electrically conducting wiremesh.

In yet another embodiment of the present invention, said circumferentialfree end portion of the second electrode may be formed out of anelectrically conducting material permeable to the sprayed liquid, e.g.some porous material.

According to a further embodiment of the present invention, the secondelectrode is arranged completely within the spray chamber, particularlyon a boundary region of an inside of the spray chamber, which boundaryregion delimits the opening of the spray chamber.

According to a further embodiment of the invention, the second electrodeis arranged along the opening of the spray chamber, wherein the secondelectrode particularly circulates along the opening of the spraychamber, i.e., is arranged circumferentially along the opening of thespray chamber.

According to a further embodiment of the present invention, the secondelectrode, particularly a free end portion protruding from the spraychamber (e.g. along the spraying direction or longitudinal axis of thedevice or spray chamber) is designed to be expandable at the targetconcerning its diameter so that a target area delimited by the secondelectrode is enlarged. For instance, the second electrode or said freeend portion may consist out of a flexible, particularly elastic orsuperelastic material (e.g. Nitinol), such that when the device ispushed out of an (e.g. extended) tubular device (see below) the secondelectrode or said free end portion of the second electrode expandsradially so as to increase said diameter of the second electrode/freeend portion of the second electrode. Likewise, when pulling the deviceback into said tubular device, the second electrode or free end portionof the second electrode is contracted radially and the diameter iscorrespondingly reduced again.

In the above case, the second electrode or free end portion of thesecond electrode is preferably self-expanding (e.g. due to itselasticity). However, in a further embodiment, the second electrode orthe free end portion of the second electrode can be designed to beexpanded and/or contracted by means of an actuation means eithermanually or automatically.

According to a further embodiment of the present invention, a connection(which may e.g. be provided by one, two or several conductors) of thesecond electrode to a voltage source (see e.g. below) and/or the secondelectrode itself is (e.g. at least partly) shielded from the firstelectrode by an electromagnetic shielding. The shielding is preferablymade out of or comprises an electrically conductive material, whereinsaid shielding is preferably electrically connected to an electricalpotential ranging from the potential of the first electrode up to apotential below the potential of the second electrode. Preferably, saidshielding as well as particularly its geometry allows forinfluencing/shaping the electrical field generated by the first andsecond electrode (and the shield), and therefore particularly allows fora control of the electrospray process.

According to an embodiment of the invention an electrically shieldedconnection of the second electrode to the voltage source in the form ofone, two or several coaxial conductors (e.g. coaxial cables) comprisingan inner conductor and an outer conductor surrounding the innerconductor, respectively, is provided, wherein the inner and the outerconductor are arranged coaxially with respect to each other, wherein thesecond electrode is connected to the respective inner conductor, whilethe respective outer conductor forming said shielding is connected to adifferent electrical potential ranging between a potential being largerthan the potential of the second electrode and the potential of thefirst electrode. In particular, the shielding may be connected to thesame potential as said first electrode.

According to yet another embodiment a cylindrical shielding (i.e. acylindrical shielding electrode) is provided, which surrounds the firstelectrode and is particularly coaxially arranged with respect to thefirst electrode. With respect to the radial direction of the cylindricalshielding, the conductor(s) connecting the second electrode to thevoltage source extend(s) adjacent to the cylindrical shielding, butoutside the cylindrical shielding.

In order to be able to observe an individual electrospray process, e.g.the formation of the droplets and their acceleration towards the target,the spray chamber particularly comprises at least one window accordingto a further embodiment of the invention.

Preferably, two such windows are provided, which face each other acrossthe spraying direction.

According to another embodiment of the invention, the second electrodecomprises at least two separate electrode elements (or even more),wherein the device is configured to switch these electrode elements soas to form a single counter electrode to the first electrode foraccelerating said droplets. Once the droplets are accelerated asintended, the device is designed to generate a potential differencebetween said electrode elements so as to generate an electroporation ofthe droplets injected into the target in addition. Preferably, theseelectrode elements face each other across the spraying direction, e.g.are distributed around the spraying direction.

Preferably, the electrode elements are formed/arranged symmetrically,e.g., in the case of two electrode elements the latter may be formed ashalf rings. In case of four electrode elements the latter may be formedas quarter rings. Generally, a number of electrode elements may beprovided which may be arranged (equidistantly distributed) one after theother along the opening of the spray chamber. The entirety of theelectrode elements then forms said contact area, particularly.

For generating the necessary potential difference, the device comprisesa (controllable) voltage source that is preferably connected viasuitable conductors (e.g. wires) extending from the voltage source tothe housing's first and second electrode(s). The housing may providesuitable contacts for these conductors. Particularly, the voltage sourceis designed to generate a high voltage (potential difference) in therange of 1 kV and 25 kV (other ranges may also prove to be suitable)between the first electrode and the second electrode(s), so as toaccelerate said droplets towards said target resulting in transfection.The voltage source may operate in a continuous or in a pulsed mode.

According to an embodiment of the present invention, the device isconfigured to set the second electrode by means of the voltage source ona potential different from ground as well as different from the firstelectrode, particularly so as to enhance electroporation of the dropletsinjected into the target by increasing a membrane potential of saidtissue (cells).

According to a further embodiment of the invention, the electrodesdescribed above are integrated into the housing resulting in a verycompact device.

According to an embodiment of the invention the housing comprises aninner part and an outer part encompassing said inner part, wherein thefirst electrode is held by said inner part and wherein the secondelectrode is held by said outer part. For this, the housing may comprisea first collet means for holding the first electrode or a conductor (forconnecting the first electrode to a voltage source) connected to thefirst electrode, wherein particularly said inner part comprises thefirst collet means, as well as a second collet means for holding atleast one conductor (e.g. two conductors) connected to the secondelectrode, wherein particularly said outer part comprises the secondcollet. Via said conductors, the second electrode can be connected tothe voltage source.

According to another embodiment of the invention, the housing or atleast a free end or face side of the housing delimiting said opening ofthe spray chamber is made out of a flexible material such as silicone inorder to reduce the risk of damaging/injuring the target when using thedevice.

According to another embodiment of the invention, the housing, the (e.g.integrated) first electrode and the second electrode may be realizedfrom flexible material to obtain a flexible device. In particular, thehousing can be made of a flexible polymer (e.g. PDMS) and the electricconductive material used for said electrodes may be a conductivepolymer, a flexible metal (e.g. a nickel titanium alloy (NiTi), alsoknown as Nitinol, which is a metal alloy of nickel and titanium, wherethe two elements are present in roughly equal atomic percentages,particularly 50% to 60% Ni and e.g. 40% to 50% Ti depending on the Niconcentration and eventually other components that may be used in a TiNialloy. NiTi alloys exhibit shape memory as well as superelasticity (alsodenoted as pseudoelasticity). Shape memory means the ability of thealloy to undergo deformation at one temperature, while the initialundeformed shape is recovered upon heating above the transformationtemperature of the alloy. Superelasticity occurs at a narrow temperaturerange just above said transformation temperature; in this case, noheating is necessary to cause the undeformed shape to recover, and thematerial exhibits enormous elasticity (e.g. 10-30 times that of ordinarymetal). Here, the NiTi alloy or another alloy is preferably chosen suchthat elasticity particularly superelasticity occurs in a temperaturerange that comprises the temperature of the target or a temperatureduring application of the electrospray device.

Said alloy may be formed in a flexible geometry (e.g. a coil). Further,besides NiTi, also metals (e.g. steel) or other alloys formed in aflexible geometry (e.g. a coil) may also be used.

Further, multiple use of the device may results in a moistening of thehousing (body), leading to an increased risk of electrical discharge.Therefore, the housing or parts thereof (particularly the spray chamber)are preferably formed out of or coated with a hydrophobic or superhydrophobic material, or contain nano- or microstructures in order toobtain hydrophobic or super-hydrophobic properties. Superhydrophobicsurfaces are highly hydrophobic. In this case the contact angle of awater droplet exceeds 150°. This is also referred to as the Lotuseffect.

According to another embodiment of the invention, the device may beformed from two-dimensional (sheet-like) material layers. For instance,the first electrode may be formed by a rolled up conductive layer.Further, the second electrode may be formed by a rolled up conductivelayer. Likewise, the housing may comprise a rolled up insulating layerrolled around the first electrode defining the spray chamber andparticularly a second insulating layer rolled around the secondelectrode (which is particularly rolled around said insulating layerdefining the spray chamber).

According to yet another embodiment of the invention, the device maycomprise a plurality of second electrodes arranged one after another inthe spray chamber along the spraying direction, wherein each twoneighboring second electrodes form a pair of electrodes, wherein thefirst pair is formed by the first electrode and the closest secondelectrode along the spraying direction. Here, the device is configuredto generate with help of the voltage source a potential differencebetween said pairs in a subsequent fashion along the spraying directionstarting from the first pair, then between the second pair and so forth,so as to accelerate said droplets between each pair of electrodes alongthe spraying direction. This configuration can be compared to aperistaltic pump and allows for a formation of the electrospray at alower voltage. In other words, the device provides for a plurality ofacceleration stages for the droplets.

According to a further embodiment of the present invention, the secondelectrode (or the plurality of second electrodes) is formed to befluidic transparent. Therefore, the second electrode(s) particularlycomprise a plurality of recesses through which said accelerated dropletscan pass the second electrode along the spraying direction on theirflight towards the target. For instance, such a second electrode may beformed as a grate or comprises at least one clamp, particularly aplurality of (e.g. parallel) clamps. This allows the second electrode toextend parallel to or in front of the opening of the housing (e.g. inthe spray chamber) without actually blocking the opening for thedroplets.

According to a further embodiment of the invention, the device comprisesa means for generating a gas flow along the spraying direction aroundthe reservoir or first electrode, particularly so as to confine thedroplets (spray) and/or reduce the risk of corona discharge and/or togenerate a defined gaseous environment within the spray chamber.Further, some gases (like carbon dioxide) have a higher dielectricstrength. Furthermore, the flow of a dry gas removes humidity and thushelps to prevent a discharge.

In this regard, the device may comprise a slit extending around thereservoir (inner part of the housing) through which said gas may flowinto (and through) the spray chamber for providing said environment.

According to yet another embodiment of the invention, the housing (body)of the device comprising the reservoir, spray chamber and electrodes isdesigned to be inserted into a working channel of an (e.g. extended)tubular device (at a distal end of the latter), wherein said tubulardevice is particularly formed as an endoscope, particularly abronchoscope. This allows one to position the housing close to therespective target (e.g. distal lung).

According to a further object of the invention, a system is proposed,comprising an (e.g. extended) tubular device, particularly in the formof an endoscope or a bronchoscope, and a device according to theinvention, wherein the housing is inserted into a working channel of thetubular device (at its distal end) for arranging said housing at thetarget.

According to a further object of the invention, a method for producing adevice according to the invention is proposes, the method comprising thesteps of:

-   -   rolling up a first conductive layer so as to form an (e.g.        cylindrical) first electrode,    -   rolling a first insulating layer around the first electrode        forming a first part of a housing of the electrospray device,        which first part delimits a spray chamber of the electrospray        device,    -   rolling a second conductive layer around said rolled first        insulating layer so as to form a second electrode, and    -   particularly rolling a second insulating layer around the second        electrode so as to form a second part of the housing.

According to a further object of the invention, a method for deliveringa substance into a cell or a plurality of cells forming a target isproposed, the method comprising the steps of: Accelerating chargeddroplets of a liquid comprising said substance out of a reservoir(storage volume) towards said target by means of an electric fieldgenerated by means of at least a first and a second electrode such thatsaid droplets or said substance contained in the droplets overcome therespective cell membrane, particularly without destroying the respectivecell, wherein said reservoir and said electrodes are arranged in orintegrated into a housing that is particularly delivered to said targetvia a (working) channel of an (e.g. extended) tubular device,particularly an endoscope, particularly a bronchoscope, beforeaccelerating said droplets towards the target. Particularly, the secondelectrode is positioned such that it contacts the target (tissue), sothat the latter forms part of the second electrode (counter electrode).Particularly, said cells are distal cells of a lung (in vivo or exvivo), particularly alveolar epithelial cells. Particularly, saidsubstance is a plasmid, wherein said plasmid can be a reporter plasmidto be used for instance in animals (e.g. as a proof of concept), andwherein preferably the plasmid may contain Human Hepatocyte growthfactor (HGF), e.g. for clinical applications to treat Pulmonary fibrosis(see above).

Further, the above described device/method may also be used/conductedwith help of an additional external ground electrode positioned belowthe target. Furthermore, one may merely use such an external groundelectrode (instead of the second electrode).

Further, the above described device/method may also be used/conductedwith help of an additional external ground electrode positioned belowthe target. Furthermore, one may merely use such an external groundelectrode (instead of the second electrode).

Furthermore, each of the following aspects of the present invention,which are also described above, may be formulated as a sub claim to theindependent claim as follows:

According to an aspect of the invention said electrodes (100, 200) areintegrated into the housing (30).

According to an aspect of the invention the housing (30) comprises aninner part (30 a) and an outer part (30 b) encompassing said inner part(30 a), wherein the first electrode (100) is held by said inner part (30a) and wherein the second electrode (200) is held by said outer part (30b).

According to an aspect of the invention the housing (30) comprises afirst collet means for holding the first electrode (100) or for holdinga conductor connected to the first electrode (100), wherein particularlysaid inner part (30 a) comprises the first collet means, and wherein thehousing (30) comprises a second collet means for holding at least oneconductor (210) connected to the second electrode (200), whereinparticularly said outer part (30 b) comprises the second collet means.

According to an aspect of the invention the housing (30) is made out ofa flexible material, particularly silicone.

According to an aspect of the invention the first electrode is formed bya rolled up conductive layer.

According to an aspect of the invention the second electrode is formedby a rolled up conductive layer.

According to an aspect of the invention the housing comprises a rolledup insulating layer rolled around the first electrode defining the spraychamber and particularly a second insulating layer rolled around thesecond electrode.

According to an aspect of the invention the second electrode (200)defines a plurality of recesses through which said accelerated droplets(D) can pass the second electrode (200) along the spraying direction(S), wherein particularly the second electrode (200) is formed as agrate or comprises at least one clamp, particularly a plurality ofclamps.

According to an aspect of the invention the device (1) comprises a meansfor generating a gas flow along the spraying direction (S) around thereservoir (10), particularly so as to confine the droplets (D) and/orreduce the risk of corona discharge and/or to generate a defined gaseousenvironment within the spray chamber (31).

According to an aspect of the invention the housing (30) of the device(1) is designed to be inserted into a working channel (501) of anextended tubular device (500), particularly in the form of an endoscope,particularly in the form of a bronchoscope, for arranging said housing(30) at the target (T).

Further, according to an aspect of the present invention a furtherindependent claim may be directed towards a Method for producing adevice for spraying charged droplets of a liquid towards a target alonga spraying direction, comprising the steps of:

-   -   rolling up a first conductive layer so as to form a first        electrode (100),    -   rolling a first insulating layer around the first electrode        (100) forming a first part of a housing (30) of the device (1),        which first part delimits a spray chamber (31) of the device        (1),    -   rolling a second conductive layer around said rolled first        insulating layer so as to form a second electrode (200), and    -   particularly rolling a second insulating layer around the second        electrode (200) so as to form a second part of the housing.

Further features and advantages of the invention shall be described bymeans of detailed descriptions of embodiments with reference to theFigures, wherein

FIG. 1 shows a concrete example of a device according to the invention;

FIG. 2 shows a schematical view of a device of the kind shown in FIG. 1;

FIGS. 3-5 show further schematical views of variants of devicesaccording to the invention;

FIG. 6 shows an exemplary set up of an electropolished conductive pipe,a standard needle, and an additional isolation (inner part of deviceaccording to FIG. 1);

FIG. 7 shows an application of a device according to the invention on anexplanted slice of lung tissue 1-3 mm thick (Adult Fischer rat, F344)within the well plate (left) and with an additional external electrode(right);

FIG. 8 shows fluorescence microscopic images of cell cultures, sprayedwith GFP 5.0 kV (upper left), 5.5 kV (upper right) and 6.5 kV (lowerleft) after 24 hours incubation;

FIG. 9 shows fluorescence microscope images of lung tissue after 24hours incubation at 37° C. GFP positive cells (green) can be observedusing the device for electrospray (left) and using an additionalexternal electrode (right);

FIG. 10 shows fluorescence microscope images with transfected alveolarepithelial type II cells (orange), in contrast to non-transfected cells(red) and GFP (green) applied by an device according to the invention(left) and with an external electrode (right);

FIG. 11-14 show possible shapes of second electrodes (contact areas);

FIG. 15 shows an example of a device according to the invention(diameter 4 mm, working distance 4 mm) and the simulated emergingelectrical field, assuming an applied voltage of 3.5 kV at the firstelectrode and ground at the second electrode;

FIG. 16 shows a further example of a device according to the invention(diameter 4 mm, working distance 4 mm), wherein a conductive shieldingis provided within the housing of the device, extending 1.6 mm axiallyinto the spray chamber (which is 40% of the working distance) andconnected to the same potential as the first electrode (3.5 kV);

FIG. 17 shows the exemplary device shown in FIG. 16, wherein theshielding is connected to a potential in between the potentials of thefirst and the second electrode, 2.5 kV in particular;

FIG. 18 shows an example of a flexible electrospray device according tothe invention, consisting of a PDMS tubing with a flexible NiTi (e.g.Nitinol) tubing providing the fluid delivery (e.g. reservoir) and as thefirst electrode, and a coil shaped conductor for connecting the secondelectrode to the voltage source;

FIG. 19 shows a close up of the tip of the reservoir of the device shownin FIG. 18; and

FIG. 20 shows a device according to the invention having through-holesin the housing connecting the spray chamber to a surrounding so thatliquid that has accumulated inside the spray chamber can be dischargedout of the spray chamber.

FIGS. 1 to 5 show devices 1 for a nonviral gene transfer to e.g. thelung tissue by the use of an electrospray process. Droplets D containinga negatively charged liquid L (e.g. a plasmid) are accelerated towards apositively charged second electrode 200 by an electrical field along aspraying direction S. In addition, the likely charged droplets D areaffected by Coulomb repulsion and explosion, and experience anadditionally accelerating force. This interaction leads to the formationof very small sized droplets D. It is to be noted, that the polarity ofthe electrodes 100, 200 as shown in the FIGS. 2 to 5 depends on thespecific liquid L and corresponds to the one used with plasmid L. Ofcourse, the polarity shown in FIGS. 2 to 5 may also be reversed (forinstance, in case of other liquids L, the second electrode 200 mayactually be negative while the first one 100 may be positive).

In case of plasmid L the positive second electrode 200 nearby thetargeted tissue (target) T guides a droplet D bombardment towards thetissue T, providing a high impact velocity for the collision with thecell membrane of the tissue T.

According to FIG. 2 showing a schematical illustration of anelectrospraying device 1 according to the invention, the device 1comprises a housing 30 for receiving the components of the device 1,particularly a reservoir 10 for providing/delivering the liquid L thatis to be sprayed into the target T along a spraying direction S (here,the reservoir 10 is a conduit being in fluid connection to a syringepump), as well as a first electrode 100 and a second electrode 200forming a contact area 200 a for contacting the tissue T, which contactarea 200 a is spaced apart along said spraying direction S (workingdistance) from an outlet 11 of the reservoir 10, which is actuallydelimited/formed by the tubular first electrode 100. The housing 30further delimits a spray chamber 31 extending along the sprayingdirection S from the outlet 11 to an opening 32 of the spraying chamber31 along which opening 32 the second electrode 200 circulates with itscontact area 200 a in an annular manner as shown in FIG. 11. Generally,the second electrode 200 may be contacted by means of two conductors 210extending along the housing 30. Said conductors 210 may also be replacedby a region (conductor) 210 of the second electrode 200 being formed asa cylinder encompassing the first electrode 100. In case of twoconductors 210, the latter are preferably symmetrically arranged withrespect to a longitudinal axis of the housing 30 extending along thespraying direction S.

The second electrode 200 serves as a ground electrode, which is used toensure the ground potential at the tissue T. Preferably, the secondelectrode 200 is integrated into the housing 30. A high voltage togenerate the electrical field is connected to the first electrode 100,which also delivers the liquid L (see above). Due to the spray chamber31 within the housing (also denoted as body) 30 a predefined workingdistance is provided between the electrodes 100, 200, and therefore,assuming constant electrical conditions within the spray chamber 31, adefined electrical field for the electrospray process. Furthermore, thespray chamber (cavity) 31 reduces the effect of changes in thesurroundings, e.g. alternating airflow due to respiration.

Now, electrospraying of the droplets D is based on the migration ofdroplets D emitted from an electrified meniscus at the outlet 11 of thereservoir 10/first electrode 100 towards the second (counter) electrode200. In this process, electrically charged droplets D are accelerateddue to the interaction with the electrical field generated by theelectrodes 100, 200 and affected by the Coulomb repulsion between thedroplets D. Additionally, these forces will disrupt the droplets D evenmore. Therefore very small droplets D, travelling at high velocities areobtained that can pass the individual cell membrane. In contrast toother aerosol generating systems, e.g. ultrasonic or pressure drivennebulizers, no mechanical movement of components or airflow is required.

FIG. 1 shows an example of a device according to FIG. 2. Here, thehousing (body) 30 was manufactured using an additive manufacturingprocesses using an Eden250™ 3D Printing System (Objet) to process aphotopolymer (FullCure®850 VeroGray from Objet).

For improved experimental flexibility the housing 30 (FIG. 2) consistsof two pieces, namely an inner part 30 a, containing a first colletmeans for the first electrode in the form of an conductive pipe 100forming also the reservoir 10, and an outer part 30 b, containing asecond collet means for an electrical connection (conductors 210) to thesecond (ground) electrode 200. To assure a symmetrical electrical fieldthe two conductors 210 provided for the ground electrode 200 aresymmetrically arranged (e.g. parallel to the spraying direction S onopposite sides of the housing 30). However, this is only one example.Instead of the two conductors 210 also a single conductor (e.g. a foilwrapped around housing 30) or even more than two conductors 210 may beused.

Furthermore, the housing 30 comprises two windows 33 in the region ofthe spray chamber 31 to be able to observe the electrospray processvisually. The outer dimensions of the body are 30 mm length by 10 mmdiameter. However, these dimensions can be tailored with respect to theactual application and are thus not fixed. Instead of such windows 33 orin addition, the spray chamber 31 may comprise a plurality ofthrough-holes H according to FIG. 20 through which liquid L that hasaccumulated in the spray chamber can be drained out of the spray chamber31.

For the ground electrode connection (conductors 210) preferablystainless steel (1.4310, Ø300 μm) is used. The ring shaped contact area(interface) 200 a of the second electrode 200 and the tissue is realizedusing a conductive paint (Graphit 33, CRC Industries).

Further, FIG. 6 shows an exemplary setup of the pipe arrangement (innerpart 30 a), wherein the conductive pipe 100 consists of a stainlesssteel tubing (SUS316L, 28G tubing, o.Ø 360 μm, i.Ø 170 μm, ˜50 mmlength) inserted for stability purposes within a standard 21G needle N.The edges of the pipe 100 are deburred by an electropolishing procedure.The pipe 100 is connected to the fluid reservoir 10 (FEP tubing) andoffers a high voltage electrical connection. Additionally, the completearrangement is insulated using heat shrink tubing 12.

The complete assembly according to FIGS. 1, 2 and 6 creates a workingdistance from the exit port (outlet 11) of the pipe (first electrode)100 to the second (counter) electrode 200 of 8 mm.

For the delivery of the liquid L to the reservoir 10, a precisionsyringe pump (cetoni neMESYS, with 500 μl glass syringe) is connected tothe pipe 100, enabling delivery of a predefined volume at a predefinedflow rate. A high voltage source (FuG HCP 35-6500 MOD, AIP Wild AG) 300(c.f. also FIG. 2) was connected to the device 1 to generate theelectrical field. It can be used in pulsed or continuous mode.

FIGS. 3 to 5 show modifications of the device 1 according to FIG. 1 (seeFIG. 2 concerning connections to a voltage source 300). According toFIG. 3 the second electrode 200 may extend along an outside of thehousing 30 along the spraying direction S with a cylindrical region 210or separate conductors 210 and reaches behind a face side 10 a of thehousing 30 delimiting the opening 32 of the spray chamber 31 so as toform a contact area (interface) 200 a for contacting the respectivetarget T. Said contact area 200 a may circulate along the opening 32,i.e., may be shaped as a ring. The second electrode 200 may have acylindrical shape encompassing the housing 30 at least at the opening 32of the spray chamber 31 or may be separated into two electrode elements200 b, 200 c at said opening 32 facing each other across the sprayingdirection S as shown in FIG. 12. Such separate electrode elements 200 b,200 c can be shaped as half rings according to FIG. 12 and may also becontacted by conductors 210 in the form of wires as described withrespect to FIGS. 1 and 2.

In case of two electrode elements 200 b, 200 c, the latter may beswitched by the device 1 to form a single second (counter) electrode 200for accelerating the droplets D. Thereafter, a potential difference isapplied to the electrode elements 200 b, 200 c by the device 1 so as togenerate electroporation for enhancing delivery of the droplets D or thesubstance contained therein into the respective cells (target T).

As shown in FIGS. 13 and 14, also more than two electrode elements 200b, 200 c can be provided. In case of FIG. 13, the second electrode 200comprises four electrode elements 200 b-200 d distributed along theperiphery of opening 32, while there are eight such electrode elements200 b-200 i in FIG. 14. The multiple electrode elements 200 b-200 d, 200b-200 i also function as a single second electrode 200 for acceleratingthe droplets D, while a potential difference may be applied afterwardsbetween these electrode elements in order to generate electroporation.

According to FIG. 4, the first electrode 100 may extend with a region110 into the spray chamber 31 such that a part of an inside 31 a of thespray chamber 31 adjacent to the outlet 11 of the first electrode (pipe)100 is covered by said region 110.

Furthermore, according to FIG. 5, the second electrode 200 may bearranged completely inside the spray chamber 31. Here, no contact ismade between the second electrode 200 and the tissue (target) T. Asbefore, the second electrode 200 being arranged along the opening 32 ofthe spray chamber 31 may circulate along the opening 32 on a boundaryregion 32 a of the inside 31 a of the spray chamber 31 in an annularmanner, which boundary region 32 a delimits the opening 32 of the spraychamber 31.

Further, the configuration according to FIG. 5 can be used for providingseveral acceleration stages for the droplets D when an (optional)plurality of second electrodes 200 (see dashed lines) is provided in thespray chamber 31 one after the other along the spraying direction S.Then, these second electrodes 200 (together with the first electrode100) can be switched in a pairwise fashion (one pair P after the otheralong the spraying direction S). For instance, initially, the first pairP formed by the pipe 100 and the adjacent second electrode 200 comprisesa potential difference that accelerates droplets D towards the opening32/target T. Then the next pair P′ is switched providing again apotential difference accelerating the droplets D that have beenaccelerated by the first pair P before and so on.

Further, transferring the electrospray process/device 1 according toFIGS. 1 to 6 into a successful therapeutic device may be achieved by theintegration of the device 1 within standard diagnostic or interventionalprocedures. For pulmonary examination this is a bronchoscope forinstance. Depending on the application, other tubular devices(endoscopes) may also be used for transporting the device 1 or ratherits housing 30 to the target T.

As shown in FIG. 2 as an example, a device 1 according to the inventionis preferably placed in a working channel 501 of such an (e.g. extended)tubular device (e.g. bronchoscope) 500 and is displaced therein towardsa distal end 502 of said tubular device 500, which distal end 501 ispositioned at the location of the target T (e.g. the distal lung forinstance). Conductors for contacting the electrodes 100, 200 of thedevice 1 according to the invention then extend from a voltage source300 through said working channel 501 towards the housing 30 of thedevice 1 arranged within the working channel 501 at the distal end 502of the tubular device 500.

Using a working channel 501 of a tubular device (endoscope) 500 providesa concept using only a single port to access the targeted region T,which is possible since the device 1/housing 30 according to theinvention incorporates all relevant functional elements (see alsoabove), i.e., at least a first and a second electrode 100, 200 forgenerating the electrical field, an acceleration stage where this fieldis applied and interacts with the liquid L, and a liquid deliverymechanism, to provide the therapeutic dissolved substance or suspension.The electrical field for acceleration is created by said electrodes 100,200, one formed by the outlet 11 of the electrically conductive pipe100, containing the liquid L to be delivered, and a counter electrode200 in contact to the tissue T, for example, thus using the targetedtissue T itself as a counter electrode.

FIGS. 16 to 17 show the calculated influence of an additional symmetric(i.e. cylindrical shielding 400 on the electrical field distribution Fshown in solid lines. Charged droplets within the spray chamber 31 willbe affected by the electrical field and will attain an acceleratingforce according the direction of the electrical field lines. Therefore,the field lines F may be roughly interpreted also as flight tracks ofthe charged droplets. In particular, FIG. 15 shows the distribution Fwithout any shielding, while the devices 1 as shown in FIGS. 16 and 17comprise a shielding 400. The shielding 400 is formed as a symmetric,particularly cylindrical conductor that surrounds the first electrode100, wherein said shielding 400 is particularly arranged coaxially withrespect to the first electrode 100 that surrounds the reservoir 10 ofthe respective device 1 as described with respect to FIGS. 1 to 5. Theshielding further extends adjacent to the second electrode 200, 210 orclose to conductors 210 connecting the second electrode 200 to thevoltage source 300, see also above. In FIGS. 16 and 17, the shielding400 extends 1.6 mm axially into the spray chamber 31, corresponding to40% of the working distance, i.e., the distance from the tip/end of thefirst electrode 100 to the target T (e.g. when the device 1 restsagainst the target T). The electrical field lines F are focused in theradial direction towards the center of the spray chamber 31 of thedevice 1, depending on the potential applied to the shielding 400. InFIG. 16 the shielding 400 assumes the same potential as the firstelectrode 100 (3.5 kV), while in FIG. 17 the shielding assumes anelectrical potential in between the potential applied to the first andthe second electrode 100, 200 (2.5 kV). The cylindrical shielding 400described with respect to FIGS. 16 to 17 may also be present in thedevices 1 shown in FIGS. 1 to 5.

FIG. 18 shows an embodiment of a flexible electrospray device 1according to the invention having a diameter of 3 mm. The housing 30 ismade of Polydimethylsiloxane (PDMS), and includes a flexible tubing,acting as first electrode 100 and providing the liquid L to the spraychamber 31 made of super-elastic Nickel titanium (Nitinol), as well as acoil shaped connection 210 to the second electrode 200. The interface ofthe second electrode (cup electrode) 200 to the target T is made ofbrass. Preferably, said liquid L can be delivered through a connectionto a syringe pump E. The device 1 further comprises a sheath slide A anda fittings holder B being the main port where the electrodes 100, 200and the liquid source enter the device, particularly comprisingconnections to a high voltage D (first electrode 100) as well as to aground electrode C being the second electrode 200, and wherein sheathslide A provides a book mark which can tell the user the approximatedepth of the device 1 inside the body into which the device is inserted.

FIG. 19 shows a close up of the tip of the flexible electrospray device1 shown in FIG. 18.

EXAMPLES A. Experimental Set Up and Procedure

We installed the device 1 according to FIGS. 1, 2 and 6 within a standand placed the target (cell culture and lung tissue) T on standard wellplates. The well plate was placed on a height adjustable platform. Theheight of the well plate was adjusted visually until the device 1 was incontact with the target (cells or tissue slice) T. The voltage was thenapplied, followed by the syringe pump. To ensure complete fluid (liquid)L delivery there was a delay of 30 seconds before switching the powersource off.

B. Cell Culture

A549 cells (alveolar epithelial like cells) were grown to confluence inRPMI growth medium with 10% fetal bovine serum (FBS) in 24-well plates(15.6 mm in diameter). Before electrospray the growth medium was removedand electrospray was performed either in absence of medium or inpresence of 100 μl of medium. For electrospraying 50 μg/ml enhancedgreen fluorescent protein (eGFP) reporter gene suspended in distilledwater was used.

The current flow during the spray process was limited to 200 μA, whilethe applied voltage was set from 5.0 to 6.5 kV. Assuming a homogenousfield distribution, this corresponds roughly to an electrical field inthe range 0.56 to 0.81 kV/mm. At a flow rate of 100 μl/min we delivered50 μL of plasmid suspension, corresponding to 2.5 μg of the plasmid. Thecell cultures were subsequently incubated for 24 hours at 37° C. with 5%CO2 and observed under a fluorescence microscope.

Additional experiments were performed, while the working distance waschanged to 3 mm, the applied voltage covered a range of 2.5 kV to 3.5kV, using a flow rate of 10 μl/min. A volume of 30 μl of plasmidsuspension (500 μg eGFP per ml H₂O) corresponding to 15 μg of theplasmid was delivered towards the target T, wherein said water wasdiluted with 0%, 3 vol %, and 30 vol % ethanol.

C. Explanted Lung Tissue

As proof of the concept on regular lung tissue, slices of explanted lung(Fischer rats, F344, thickness 1-3 mm) were used. The tissue was placedwithin a 6-well plate with DMEM growth medium with 10% FCS (FIG. 7left).

Before applying the electrospray, the growth medium was removed, andonly the tissue remained. For electrospraying 50 μg/ml enhanced greenfluorescent protein (eGFP) reporter gene suspended in distilled waterwas used.

The current was limited to 200 μA, while a potential of 4.5 kV wasapplied. At a flow rate of 100 μL/min a plasmid volume of 50 μL (2.5 μgplasmid) was delivered. The lung tissue was kept for 24 hours at 37° C.,with 5% CO₂ subsequently.

For comparison a second test was performed by applying an externalelectrode E to the tissue, disabling the integrated ground electrode 200(FIG. 7 right).

Additional experiments were performed, while the working distance waschanged to 3 mm, the applied voltage covered a range of 2.5 kV to 3.5kV, using a flow rate of 10 μl/min. A volume of 30 μl of plasmidsuspension (100 μg eGFP per ml H₂O) corresponding to 3 μg of the plasmidwas delivered towards the target T. The water in the delivered media wasadditionally diluted with 3%; 9 vol % and 15 vol % ethanol.

Results

A. Cell Culture

Using a potential from 5 to 6.5 kV the transfection of eGFP (greenfluorescent protein plasmid) DNA can be observed using a fluorescencemicroscope. Shown in FIG. 8 the greenish spots 600 (one such spot isindicated by a white arrow as an example) represent single cells withtransfected reporter gene. However, the transfection rate is quite poor,a transfection of GFP can clearly be observed. An improvement oftransfection rate can be observed when increasing the potential.

The additional experiments provided an improved stability of theelectrospray process. Transfection was observed in all threeconcentrations, wherein the highest concentration of green fluorescencewas observed at a concentration of 3 vol %.

B. Ex-Vivo Lung Tissue

FIG. 9 (left) shows the fluorescence microscope images of the rat lungtissue, using an electrical potential of 4.5 kV. The greenish spots 600(one such spot is indicated by a white arrow as an example) indicate thesuccessful transfection of eGFP into the cells. The transfection rate isslightly higher as compared to the transfection of cell culture, even atlower applied potential. The fluorescence microscope image of theexperiment with the external electrode E is shown in FIG. 9 (right).

To confirm the cell type transfected, a co-staining with surfactantprotein C (SpC) antibody was performed. There were a number of doublestained cells (eGFP: green spots 600 (one such spot is indicated by awhite arrow as an example); SpC: red spots 601 (one such spot isindicated by a white arrow as an example), co-stained: orange spots 602(one such spot is indicated by a white arrow as an example)), in thetissue slice as shown in FIG. 10. This proves that we are able totransduce the alveolar epithelial cells with this technique.

Furthermore, this concept can be also adopted to be used for minimallyinvasive approach in other organ systems too.

Fluorescence analysis of the additional experiments showed thatincreasing the ethanol concentration up to 15 vol % also increases thetransfection efficiency of eGFP.

REFERENCES

-   [1] A. Gazdhar, P. Fachinger, C. van Leer, J. Pierog, M. Gugger, R.    Friis, R. A. Schmid, and T. Geiser, “Gene transfer of hepatocyte    growth factor by electroporation reduces bleomycin-induced lung    fibrosis,” Am J Physiol Lung Cell Mol Physiol, vol. 292 pp. L529-36    February 2007.-   [2] D. Soden, M. Sadadcharam, J. Piggott, A. Morrissey, C. G.    Collins, and G. C. O'Sullivan, “An endoscopic system for gene & drug    delivery directly to intraluminal tissue,” in 11^(th) Mediterranean    Conference on Medical and Biomedical Engineering and Computing 2007.    vol. 16, R. Magjarevic, Ed.: Springer Berlin Heidelberg, 2007, pp.    628-628.-   [3] Y. Okubo, K. Ikemoto, K. Koike, C. Tsutsui, I. Sakata, O.    Takei, A. Adachi, and T. Sakai, “DNA Introduction into living cells    by water droplet impact with an electrospray process,” Angewandte    Chemie, vol. 120, pp. 1451-1453, 2008.-   [4] D.-R. Chen, C. Wendt, and D. Y. H. Pui, “A novel approach for    introducing bio-materials into cells,” Journal of Nanopartical    Research, vol. 2, pp. 133-139, 2000.

The invention claimed is:
 1. Device for spraying charged droplets of aliquid towards a target along a spraying direction, comprising: areservoir (10) for receiving the liquid (L), a first electrode (100)being arranged at an outlet (11) of said reservoir (10), a secondelectrode (200) forming a counter electrode to the first electrode (100)for accelerating said droplets (D) along the spraying direction (S), anda housing (30) holding the reservoir (10) as well as said electrodes(100, 200), wherein said housing (30) forms a spray chamber (31)extending along the spraying direction (S), wherein the reservoir (10)is connected to the spray chamber (31) via said outlet (11), and whereinthe spray chamber (31) comprises an opening (32) facing said outlet (11)along the spraying direction (S) for electing the droplets (D) out ofthe spray chamber (31).
 2. Device as claimed in claim 1, characterizedin that an end region (200 a) of the second electrode (200) is spacedapart from said outlet (11) along the spraying direction (S).
 3. Deviceas claimed in claim 1, characterized in that the first electrode (100)comprises a tubular shape.
 4. Device as claimed in claim 1,characterized in that the first electrode (100) extends into the spraychamber (31), wherein the first electrode (100) comprises a region (110)arranged on an inside (31 a) of the spray chamber (31) extending alongthe spraying direction (S).
 5. Device as claimed in claim 1,characterized in that the second electrode (200) is arranged at least insections on a face side (10 a) of the housing (30) delimiting saidopening (32).
 6. Device according to claim 1, characterized in that thespray chamber (31) comprises a plurality of lateral through-holes (H)for discharging liquid (L) accumulated in the spray chamber (31) out ofthe spray chamber (31).
 7. Device as claimed in claim 1, characterizedin that the second electrode (200) comprises a contact area (200 a)being designed to contact said target (T) into which said liquid (L) isto be injected.
 8. Device according to claim 1, characterized in that,the second electrode (200) comprises a circumferential free end regionprotruding from or out of the spray chamber (31), which free end regionforms a contact area (200 a) being designed to contact said target (T)into which said liquid (L) is to be infected.
 9. Device as claimed inclaim 1, characterized in that the second electrode (200) is arrangedwithin the spray chamber (31).
 10. Device as claimed in claim 1,characterized in that the second electrode (200) is arranged along theopening (32) of the spray chamber (31), wherein the second electrode(200) extends circumferentially along the opening (32) of the spraychamber (31).
 11. Device according to claim 1, characterized in that thesecond electrode (200) or a free end region of the second electrode(200) protruding from the spray chamber (31) is designed to be expandedfrom a first state into a second state and contracted from the secondstate into the first state, wherein the second electrode (200) or saidfree end region comprises a larger diameter in the second state than inthe first state, wherein the second electrode (200) or said free endportion is designed to be expanded from the first into the second state,when the second electrode (200) or said free end portion is pushed outof a working channel (501) of a tubular device (500), wherein the secondelectrode (200) or said free end portion is designed to be contractedfrom the second state into the first state, when the second electrode orsaid free end portion is pulled into a working channel (501) of atubular device (500), wherein the second electrode (200) or said freeend portion is made of or comprises a flexible, electrically conductivematerial, wherein the second electrode (200) or said free end portion isself-expanding or wherein the device (1) comprises an actuation meansfor expanding and/or contracting the second electrode (200) or said freeend portion.
 12. Device according to claim 1, characterized in that aconnection (210) of the second electrode (200) to a voltage source (300)and/or the second electrode (200) is shielded from the first electrode(100) by a shielding (400), wherein said shielding (400) is connected toan electrical potential ranging from a potential of the first electrode(100) up to a potential below the potential of the second electrode(200).
 13. Device according to claim 12, characterized in that aconnection (210) of the second electrode (200) to the voltage source(300) comprises an inner conductor and an outer conductor surroundingthe inner conductor, wherein the inner and the outer conductor arearranged coaxially with respect to each other, wherein the secondelectrode is connected to the respective inner conductor, while therespective outer conductor forming said shielding is connected to adifferent electrical potential in between the potential of the secondelectrode and the potential of the first electrode.
 14. Device accordingto claim 12, characterized in that said shielding (400) is a cylindricalshielding which surrounds the first electrode (100) and is coaxiallyarranged with respect to the first electrode (100).
 15. Device asclaimed in claim 1, characterized in that the spray chamber (31)comprises at least one window (33).
 16. Device according to claim 1,characterized in that the second electrode (200) comprises at least twoseparate electrode elements (200 b-200 i), wherein the device (1) isconfigured to switch the at least two electrode elements (200 b-200 i)so as to form a single counter electrode to the first electrode (100) inorder to accelerate said droplets (D), wherein—after having acceleratedsaid droplets (D)—the device (1) is further designed to apply apotential difference between the at least two electrode elements (200b-200 i) for additional electroporation of the droplets (D) injectedinto the target.
 17. Device according to claim 1, characterized by avoltage source (300) connected to the first and the second electrode(100, 200), which voltage source (300) is designed to generate apotential difference between the first electrode (100) and the secondelectrode (200) so as to accelerate said droplets (D) towards saidtarget (T), wherein the voltage source (300) is designed to generatesaid potential difference as a continuous potential difference or apulsed potential difference.
 18. Device as claimed in claim 1,characterized in that the device (1) is configured to set the secondelectrode (200) on a potential different from ground and different fromthe first electrode (100), so as to enhance electroporation of thedroplets (D) injected into the target (T) by increasing a membranepotential of said target (T).
 19. Device as claimed in claim 1,characterized in that the device (1) comprises a plurality of secondelectrodes (200) arranged one after another along the spray chamber (31)along the spraying direction (S), wherein each two neighboring secondelectrodes (200) form a pair (P, P′) of electrodes, wherein the firstpair (P) is formed by the first electrode (100) and a neighboring secondelectrode (200) along the spraying direction (S), and wherein the device(1) is configured to generate a potential difference between said pairs(P, P′) in a subsequent fashion along the spraying direction (S)starting from the first pair (P) so as to accelerate said droplets (D)between each pair (P, P′) of electrodes along the spraying direction(S).
 20. Device according to claim 1, characterized in that the device(1) is flexible, wherein the housing (30), the first electrode (100) andthe second electrode (200) are made out of a flexible material,respectively.
 21. Device according to claim 1, characterized in that thehousing (30) or parts thereof are formed out of or are coated with ahydrophobic or super hydrophobic material, or contain nano- ormicrostructures so as to exhibit hydrophobic or super-hydrophobicproperties.
 22. System comprising a tubular device, in the form of anendoscope or a bronchoscope, and a device (1) according to claim 1,characterized in that the housing (30) is inserted into a workingchannel (501) of the tubular device (50) for arranging said housing (30)at the target (T).
 23. Device for spraying charged droplets of a liquidtowards a target along a spraying direction, comprising: a reservoir(10) for receiving the liquid (L), a first electrode (100) beingarranged at an outlet (11) of said reservoir (10), a second electrode(200) forming a counter electrode to the first electrode (100) foraccelerating said droplets (D) along the spraying direction (S), and ahousing (30) holding the reservoir (10) as well as said electrodes (100,200), wherein the second electrode (200) comprises a contact area (200a) being designed to contact said target (T) into which said liquid (L)is to be injected, and wherein the second electrode (200) comprises acircumferential free end region protruding from or out of the spraychamber (31), which free end region forms said contact area (200 a). 24.Device for spraying charged droplets of a liquid towards a target alonga spraying direction, comprising: a reservoir (10) for receiving theliquid (L), a first electrode (100) being arranged at an outlet (11) ofsaid reservoir (10), a second electrode (200) forming a counterelectrode to the first electrode (100) for accelerating said droplets(D) along the spraying direction (S), and a housing (30) holding thereservoir (10) as well as said electrodes (100, 200), wherein aconnection (210) of the second electrode (200) to a voltage source (300)and/or the second electrode (200) is shielded from the first electrode(100) by a shielding (400), wherein said shielding (400) is connected toan electrical potential ranging from a potential of the first electrode(100) up to a potential below the potential of the second electrode(200).